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CIE Nov 2015 v2 Paper 2 Q2
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![Chemical reactions are accompanied by enthalpy changes. PMT (a) Explain the meaning of the term standard enthalpy change of reaction.[2] (b) The enthalpy change of hydration of anhydrous magnesium sulfate, Hhyd MgSO4, can be calculated by carrying out two separate experiments. In therst experiment 45.00 g of water was weighed into a polystyrene cup and 3.01 g of MgSO4 was added and stirred until it was completely dissolved. The temperature of the water rose from 23.4 C to 34.7 C. (i) Calculate the amount of heat energy transferred to the water during this dissolving process. You can assume that the speci c heat capacity of the solution is the same as that of water, 4.18 J g1 K1. (ii) Calculate the amount, in moles, of MgSO4 dissolved. heat energy =J [1] amount =mol [1]UCLES 2015 9701/22/O/N/15<br />
(iii) Calculate the enthalpy change of solution, Hsoln, of MgSO4(s). You must include a sign with your answer. PMT Hsoln, of MgSO4(s) =kJ mol1 [1] In the second experiment, the enthalpy change of solution for the hydrated salt, MgSO4.7H2O(s), was calculated and found to be +9.60 kJ mol1. (iv) Use the equation below for the hydration of anhydrous magnesium sulfate to construct a suitable, fully labelled energy cycle that will allow you to calculate the enthalpy change for this reaction, Hhyd MgSO4. MgSO4(s) + 7H2O(l)MgSO4.7H2O(s) (v) Calculate the enthalpy change for this reaction, Hhyd MgSO4. Include a sign in your answer. [1]UCLES 2015 9701/22/O/N/15 Hhyd MgSO4 =kJ mol1 [1] [Total: 7] [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v2_QP_-_Paper_2_CIE_Chemistry_A-level_2-0.jpg)
![Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A LevelOctober/November 2015 9701 22 Question Mark Scheme (ii) M1 HCl polar / has a dipole AND F2 non-polar / has no dipole OR (permanent) dipole (-dipole) attractions / forces between HCl (molecules) AND induced dipole (-induced dipole) attractions / forces / LDFs between F2 (molecules) M2 more energy needed for HCl than F2 OR pd-pd forces stronger than id-id forces OR IMFs / VdWs in HCl stronger than in F2 (iii) Hydrogen bonding (between methanol molecules) Stronger than IMFs / van der Waals in other three / is the strongest intermolecular force (a) M1 Heat (energy) change (or HprodHreact) measured at constant pressure OR enthalpy change when the amount/moles of reactants as shown in a (reaction) equation react together to give products M2 measured at standard conditions (b) (i) q = 2125.53 (ii) amount = 0.025(0) (iii) 85.(0) PMT Mark Total [1] [1] [1] [1] [2] [2] [17] [1] [1] [2] [1] [1] [1] [1] [1] [1]Cambridge International Examinations 2015<br />
Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A LevelOctober/November 2015 9701 22 Question Mark Scheme (iv) ( MgSO4(s) + 7H2O(l)MgSO4.7H2O(s) ) PMT Mark Total 85.0 (kJ mol 1 ) (+)9.60 (kJ mol 1 [1] [1] MgSO4(aq) (v) H + 9.6 = 85.0 H = 85.09.6 = 94.6 (kJ mol (a) (i) Na2O or Na2O2; MgO; P4O10 or P4O6 ; SO2 (ii) Na: Yellow / orange / gold flame / white solid / powder / smoke 4Na + O22Na2O or 2Na + O2Na2O2 S: Blue flame / (yellow) solid melts / turns red / amber / white fumes S + O2SO2 (b) (i) acidic P and S amphoteric Al and basic Na and Mg (ii) acidic: covalent (bonding) basic: ionic (bonding)Cambridge International Examinations 2015 [1] [1] [7] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [2] [4] [2] [2]<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v2_MS_-_Paper_2_CIE_Chemistry_A-level_2-0.jpg)
